BANGKOK — An oil spill that leaked from a pipeline has reached a popular tourist island in Thailand's eastern sea despite continuous attempts to clean it up over the weekend, officials said Monday.

About 50 tons of crude oil spilled into the sea off Rayong province Saturday morning after a leak sprung in a pipeline operated by PTT Global Chemical Plc, a subsidiary of state-owned oil and gas company PTT Plc.

Streaks of crude oil about 300 meters (984 feet) wide have marred the shore of Prao Bay on Samet Island, one of the most popular beach destinations among Thai and foreign tourists in the Gulf of Thailand, Rayong's deputy provincial governor Supeepat Chongpanish said on Monday.

He said authorities have closed down the bay as 300 workers are working to remove the oil from the white beach and from the waters. Tourists have been warned against going near the area.

"The top priorities right now are to get rid of the oil on the sand and the seawaters, and to make sure the spill doesn't spread to other shores," Supeepat said. "This is a very beautiful, white, sandy beach, so we want to make the spill go away as soon as possible."

The nearby area has been declared a disaster zone by provincial authorities, and those affected by the spill will receive immediate assistance.

The company said it detected the leak when the crude oil from a tanker moored offshore was being transferred to the pipeline, 20 kilometers (11 miles) away from delivery at the refinery in Map Ta Phut, one of the largest industrial estates in Southeast Asia.

The company said in a statement Sunday that it had flown in an oil spill management experts and a plane from Singapore to get rid of the crude oil. The Thai Navy vessels also joined the cleanup efforts.

The refinery on the shore was not affected by the leak.

In 2009, another PTT subsidiary was involved in the Montara oil spill, one of the Australia's worst oil disasters, in the Timor Sea off western Australia.